As water droplets form in the atmosphere around dust or other particulates, they often become visible to the naked eye forming massive clouds. At any given moment, about one half of the surface of the Earth is surrounded by a cover of clouds.
These clouds are physical evidence for the condensation processes that are taking place high above us in the atmosphere. Often the water droplets in clouds freeze forming ice crystals.
There are three main types of clouds. Each of these cloud types are similar to each other in important ways, but also are different enough that they are justified as having their own name. These three cloud types are cirriform clouds, stratiform clouds, and cumuliform clouds. Often clouds form as one type and then later transform into another.
Cirriform clouds are thin wispy clouds that streak across the sky. They are comprised mainly of ice crystals.
Stratiform clouds are found high in the atmosphere, and appear as large gray sheets covering everything in sight.
Cumuliform clouds are massive billowing clouds that often extend to great altitudes.